Optical Head

ABSTRACT

An optical head includes a mount material  30  having an optical element  10  fixed thereto and a mount material  40  having an optical fiber array  20  fixed thereto. An optical fiber  21 , which is included in the optical fiber array, is optically connected to the optical element  10 . An angle formed between the light emission receiving face  10   a  of the optical element  10  and an inclined face of the mount material  40  is 1-8 degrees.

CROSS REFERENCE TO RELATED APPLICATION

This application is a continuation of U.S. application Ser. No.09/812,721, filed Mar. 20, 2001, now U.S. Pat. No. 6,644,867, theentirety of which is incorporated herein by reference.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to an optical head comprising mountmaterials onto which an optical element and an optical fiber array arefixed, more particularly to such optical heads including an angle formedbetween a light emitting/receiving face of the optical element and aninclined face of a mount material for fixing the optical fiber array.

2. Description of Related Art

A conventional optical head includes a mount material for fixing anoptical element, such as a light receiving element or light emittingelement and a mount material for fixing an optical fiber array to whichan optical fiber is connected, and the optical fiber is opticallyconnected to the optical element.

FIG. 3 shows an optical head having a conventional light emittingelement. An LD array 10 is provided such that a plurality of laserdiodes are transversely arranged. A mount material 30 is made of a AINceramics with high heat conductivity, metalization for soldering isapplied to its surface, and a wiring, pattern 31 and a drive IC 35bonded by an electrode of the LD array 10 and a wire 32 are arranged.The LD array 10 is fixed to the mount material 30 by means of solderingso that light emissions ejected from the LD array 10 are generallycoincident with each other.

An optical fiber array 20 includes at least one V groove 23 provided ona support substrate 22 in order to position an optical fiber 21, and aplurality of optical fibers 21 are arranged to be housed in the Vgrooves 23. These optical fibers are covered with a cap substrate 24from the top, and are fixed by sheet shaped soldering, thereby formingan integral block 25.

At a position between the optical fiber array 20 and the LD array 10optically coupled with each other, a support substrate 22 is protrudedon the top face of a mount body 40; a spacer portion 34 is extruded onthe side face of the mount material 40, and the spacer portion 34 isbonded with the side face of the mount body 40. In addition, thisoptical head is sealed with air tightness in a package by leading out anoptical fiber or lead wire, whereby a parallel light transmission moduleis provided. In addition, an end face 20 a of the optical fiber 21, withwhich the LD array 10 is optically coupled, is positioned at an end faceof a block 25, and is formed so as to be opposed to a light emissionplane 10 a of the mount material 30 having the LD array 10 mountedthereon.

Next, in order to directly emit light from a light emitting element to alarge diameter end face of an optical fiber or to emit the lightexpanded or contacted by a lens, an interval between a light emissionelement required for fine adjustment and the end face of the opticalfiber is spaced, adjusted, and fixed when a connection face betweenmounted materials fixed to each other is defined as a reference. Thisderives from light intensity in a direction orthogonal to an opticalaxis of an optical element for example, a laser diode and lightintensity averaging between a plurality of fibers of the optical headafter light axis alignment.

That is, the light intensity in a direction orthogonal to an opticalaxis of a laser diode draws a Gaussian curve shape when an optical axisis defined as a center axis. However, when a point orthogonal to theoptical axis is spaced from a laser diode, a top of the curve islowered, and the gradient is gentle. When the top of the curve is low,light intensity is lowered. On the other hand, when the gradient isgentle, even if slight deviation from the optical axis occurs in avertical direction, it indicates that a small rapid change occurs withlight intensity.

In addition, in the optical head, even if the same optical intensity isinput to a plurality of configured fibers, large deviation in lightintensity must not be present between fibers due to deviation from thelight axis.

The arrangement precision of a plurality of optical elements and thearrangement precision of a plurality of fibers must be permitted to someextent in view of manufacture. This means that another optical elementand an optical fiber deviation from an optical axis even if an arbitraryoptical element and the corresponding optical fiber are completelyaligned with the axis. Even under such circumference, as means forpreventing large deviation in light intensity between fibers, there hasbeen conventionally performed means for spacing an optical element andan optical fiber from each other by a predetermined value. This methodutilizes the fact that, although light intensity is lowered as deviationfrom an optical element is more significant as described above, thevariation rate of light intensity in a direction vertical to an opticalaxis is gentle.

Specifically, a light emission element is fixed to a mount material bymeans of soldering; an optical fiber is pressed by from the top arrangedand housed in a support substrate having a V groove punched thereon, andis fixed by means of soldering; and the support substrate is fixed to atop face of the mount material. At this time, when an end face of themount material fixing an optical fiber array is defined as a referenceface, the fixing position of the light emission element is adjusted bythe mount material via a spacer for ensuring a design space. Inaddition, the position of a support substrate is fine adjusted whilesensing the light receiving capability of an optical fiber fixed to thesupport substrate against the adjustment light from the light emissionelement.

However, in order to ensure this spacing distance, positional adjustmentis cumbersome because it is intensively influenced by the dimensionalprecision of a spacer and the positional precision on the mount materialfor the light emission element. Thus, there has been a growing need forimprovement of means capable of simplifying positional adjustment usingcheck light by improving precision of adjustment technique utilizing areference face of the mount material.

SUMMARY OF THE INVENTION

According to a first aspect of the present invention, there is providedan optical head including a mount material for fixing an optical elementand a mount material for fixing an optical fiber array. The opticalfiber is optically connected to the optical element. An angle formedbetween a light emission/receiving face of the optical element and aninclined face of the mount material for fixing the optical fiber arrayis 1 to 8 degrees. In this manner, an angle formed between a lightemission/receiving face and an end face of an optical fiber is greaterthan 1 degree. Thus, noise produced by reflection light deriving from alight receiving face or an end face of an optical fiber opposed to alight emitting/receiving element is reduced as compared with a case inwhich the conventional light emission/receiving face and the end face ofthe optical fiber are substantially parallel to each other, and afailure with optical signal transmission can be prevented. In addition,an angle formed between the light emission/receiving face and an endface of the optical fiber is smaller than 8 degrees, and thus, bondingefficiency is improved. In addition, an end face can be shaved with highprocessing precision, and thus, the shaved portion can act as the abovespacing distance. Therefore, the spacing distance can be ensured withhigh precision.

According to a second aspect of the present invention, there is providedan optical head wherein thermal expansion rates of the mount material ofthe optical element and the mount material of the optical fiber arrayare substantially equal to a thermal expansion rate of the optical fiberarray material. In this manner, the thermal expansion rates of mountmaterials is substantially identical to each other. Thus, even if thesematerials are used under severe environments such that a temperaturedifference is large, there is no thermal contraction difference betweenthe mount materials, and an axial deviation in optical signals fixedthereto and transmitted does not occur.

Further, according to a third embodiment of the present invention, thereis provided an optical head wherein the optical fiber is a single mode,and the mount material of the optical element and the mount material ofthe optical fiber array are spot welded, such as Yag melded to eachother. In this manner, a single mode optical fiber of 5 to 8 microns incore diameter is smaller in core portion diameter than a multiple modeoptical fiber of 50 to 62.5 microns in diameter, the countdowndimensional precision up to sub-micron units can be precisely performedduring adjustment. Moreover, the same kinds of mount materials are used.Thus, a thermal shrinkage difference is small, and an axial deviation inoptical signals fixed thereto and transmitted does not occur.

Additional objects and advantages of the invention will be set forth inthe description which follows, and in part will be obvious from thedescription, or may be learned by practice of the invention. The objectsand advantages of the invention may be realized and obtained by means ofthe instrumentalities and combinations particularly pointed outhereinafter.

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS

The accompanying drawings, which are incorporated in and constitute apart of the specification, illustrate presently preferred embodiments ofthe present invention and, together with the general description givenabove and the detailed description of the preferred embodiments givenbelow, serve to explain the principle of the present invention.

FIG. 1 is an illustrative view illustrating an optical head having alight emitting/receiving element according to the present invention;

FIG. 2 is a perspective view showing an optical head having the lightemitting/receiving element shown in FIG. 1; and

FIG. 3 is an illustrative view illustrating a conventional optical headhaving a light emitting/receiving element.

DETAILED DESCRIPTION OF THE INVENTION

Reference will now be made in detail to the presently preferredembodiments of the invention as illustrated in the accompanyingdrawings, in which like reference numerals designate like orcorresponding parts.

Hereinafter, preferred embodiments of the present invention will bedescribed with reference to the accompanying drawings. FIG. 1 is anillustrative view illustrating an optical head having a lightemitting/receiving element according to the present invention. FIG. 2 isa perspective view showing the optical head.

The optical head includes an LD array 10, which is driven by an IC andemits light. An optical fiber array 20 arranges and fixes a plurality ofoptical fibers 21. A mount material 30 fixes the LD array 10, and amount material 40 fixes the optical fiber array 20. The optical head isoptically coupled with an optical fiber 21 in the LD array 10.

The LD array 10 has a plurality of semiconductor lasers transverselyarranged thereon. The mount material 30 is made of a SiC ceramics withhigh thermal conductivity, metalization for soldering is applied ontoits surface, and a wiring pattern 31 bonded by an electrode of the LDarray 10 and a wire 32 is arranged. The light is ejected from the LDarray 10, which is fixed to the mount material 30 by means of solderingwith the LD arrays 10 being aligned on their end faces so as to begenerally horizontal in a horizontal direction.

A V groove 23 is punched on a support substrate 22 in order to positionan optical fiber 21. A plurality of optical fibers 21 are housed andarranged on V groove 23, and a cap substrate 24 is covered over thefibers and fixed by sheet shaped soldering, thereby forming an integralblock 25. Then, at a position at which the optical fiber array 20 andthe LD array 10 are optically coupled with each other, a mount material30 of the LD array 10 is bonded with the side face of the mount body 40at a spot welding portion 41 by Yag lasers. This bonding is done by spotwelding, and thus, there is no substantial welding strain, and desiredoptical coupling does not break.

In addition, this optical head is sealed with air tightness in a packageby leading out an optical fiber or lead wire, whereby a parallel lighttransmission module is provided.

An end face 21 a of the optical fiber 21 with which the LD array 10 isoptically coupled is positioned on an inclined face of a block 25. Aninclined angle θ is defined as 2 degrees relevant to the lightemitting/receiving plane of the mount material having the opposite LDarray 10 mounted thereon. This inclined angle θ is properly 1 to 8degrees. When an angle formed between a light emitting/receiving face 10a and the end face 21 a of the optical fiber 21 is greater than 1degree, a desired spacing distance can be ensured. In addition, incomparison with the fact that a conventional light emission/receivingface and an end face of the optical fiber are substantially parallel toeach other, noise produced by reflection light deriving from the endface of the optical fiber opposed to the light emitting/receivingelement is reduced. Accordingly, a failure with optical signaltransmission can be prevented. Moreover, a gap can be formed by shavingthe end face with high processing precision. Still moreover, the angle θformed between the light emission/receiving face 10 a and the end face21 a of the optical fiber is smaller than 8 degrees, and thus, couplingefficiency is improved. The shown inclined angle θ is indicated in anexaggerated manner, and a two-dot chain line indicates the external lineof a conventional box-shaped block.

With respect to this inclined face, after a block 25 is integrallyformed to be in a box shape, an end of the optical fiber 21 protrudingfrom the block 25 is cut, and at the same time, an inclined face isshaved. In addition, its inclined face is optically ground and finished.In this manner, alignment with the LD array 10 is facilitated when themount body 40 fixing the block 25 is defined as a reference face, and agap between the LD array 10 and the end face of the optical fiber 21 canbe easily adjusted by adjusting a shaving angle of the inclined face.

As has been described above, an optical head according to the presentinvention is capable of reducing noise produced by reflection lightderiving from an end face of an optical fiber opposed to a lightreceiving face or light emitting element as compared with a conventionaloptical head in which a light emission/receiving face and an end face ofan optical fiber are substantially parallel to each other; preventing anoptical signal transmission failure; and shaving an end face with highprocessing precision. In addition, an angle formed between the lightemission/receiving face and the end face of the optical fiber is smallerthan 8 degrees, and thus, an optical head with high coupling efficiencycan be provided without using a spacer.

Additional advantages and modifications will readily occur to thoseskilled in the art. Therefore, the invention in its broader aspect isnot limited to the specific details and representative embodiments shownand described herein. Accordingly, various modifications may be madewithout departing from the spirit or scope of the general inventiveconcept as defined by the appended claims and their equivalents.

What is claimed is:
 1. An optical head comprising a mount material forfixing an optical element and a mount material for fixing an opticalfiber array, the optical fiber array being optically connected to theoptical element, wherein an angle formed between a lightemission/receiving face of the optical element and an inclined face ofthe mount material for fixing the optical fiber array is 1 to 8 degrees.